LAS VEGAS (AP) — Authorities in Las Vegas on Wednesday were investigating whether a two-alarm blaze that reduced a nearly completed, two-story mosque to ashes was arson or an accident.

No suspects were seen in the area and no injuries were reported after firefighters spent four hours dousing the intense flames, Clark County Fire Chief Bertral Washington said, as federal Bureau of Alcohol, Tobacco, Firearms and Explosives agents searched for evidence at the dusty, sprawling industrial site northeast of downtown.

An FBI agent also questioned contractors on the job, who later declined to be interviewed by The Associated Press.

“They’re investigating whether it was arson, a hate crime or something like that,” said Aslam Abdullah, director of the Islamic Society of Nevada. “We hope it was not.”

Abdullah said construction of the building began more than a year ago, and it was slated to open this year as a funeral gathering center for services at the first dedicated Islamic cemetery in the Las Vegas area.

Abdullah put the number of Muslim residents at about 18,000 in the metropolitan area with a population of about 2 million. He said society members come from more than 70 ethnic groups and dozens of countries around the world.

County spokeswoman Stacey Welling said plans called for the nearly 10,500-square-foot building and surrounding 4.6 acres to include a cemetery of just under an acre.

Khalid Khan, society president since 1986, said he was saddened by the fire but called it too early to make any judgment about a cause. He said investigators told him that they thought vandals might be to blame.

“They believe it was not an accident,” Khan said.

Washingtonsaid there was no electricity or natural gas service to the building, which workers said was about 80 percent complete. The chief estimated the loss at about $1.5 million.

ATF supervisor Thomas Chittum III said it could take several days to determine whether the fire was an accident, an act of vandalism or a crime committed against a house of worship.

“Given the religion that’s involved, we just want to make sure.” Washington said after officials surveyed the charred and bent steel beams left standing at the site.

The two-story building with a modest tower dome was fully ablaze when passers-by called 911 and firefighters arrived about 1 a.m. at the site, the fire chief said.

Two fire hydrants on the site weren’t operational, and firefighters had to stretch hoses several hundred yards to fetch water to battle flames.

Las Vegas police stopped and arrested a man in his 30s in a vehicle near the scene while firefighters were battling the fire. But Officer Bill Cassell, a department spokesman, said the man was held on traffic warrants and wasn’t a suspect in the fire.

Clark County Commissioner Tom Collins, a Democrat who represents the area, issued a statement expressing concern about the fire, relief that no one was hurt and confidence that investigators would find the cause.